contronym

A contronym or antagonym is a word that is its own antonym, that is, a word that generates two opposite meanings, such as fix, which means to restore or to castrate. A contronym may be the result of a historical process whereby a word's meaning shifts so radically that it reverses. This is known as semanticreversal, and a good example is manufacture, which originally meant to make by hand but now means to make by machine. In the case of a contronym, the new meaning does not replace the old one; rather, the two co-exist. A contronym may also occur when two separate words with opposite meanings become pronounced in the same way. An example is the word cleave, which means to adhere and also to separate; the original Old English words were cleofian and cle-ofan respectively. The A.Word.A.Day mailing which introduced this word into my vocabulary notes that contronyms are also called Janus-faced words, after the Roman god Janus who had two faces that looked in opposite directions.

Fun with Words at http://rinkworks.com/words/contronyms.shtml has a long list of contronyms, some hightlights of which are

"Take this word: 'grok.' Its literal meaning, one which I suspect goes back to the origin of the Martian race as thinking creatures--and which throws light on their whole 'map'--is easy. 'Grok' means 'to drink.'"

"Huh?" said Jubal. "Mike never says 'grok' when he's just talking about drinking. He--"

"Just a moment." Mahmoud spoke to Mike in Martian.

Mike looked faintly surprised. "'Grok' is drink."

"But Mike would have agreed," Mahmoud went on, "if I had named a hundred other English words, words which we all think of as different concepts, even antithetical concepts. 'Grok' means all of these. It means 'fear,' it means 'love,' it means 'hate'--proper hate, for by the Martian 'map' you cannot hate anything unless you grok it, understand it so thoroughly that you merge with it and it merges with you--then you can hate. By hating yourself. But this implies that you love it, too, and cherish it and would not have it otherwise. Then you can hate--and (I think) Martian hate is an emotion so black that the nearest human equivalent could only be called mild distaste."

There you have it. 'Grok' is its own antonym for hundreds of concepts, with the exception of one: Understanding. 'Grok' fundamentally requires understanding, but is not a beefed up version of it, it is in fact an entirely new concept.

The Martian custom of 'grokking' an individual is at its heart a wake combined with ritual cannibalism. All the deceased individual's closest friends (water brothers) would get together and eat his body. In the process, they would pause occasionally to praise or condemn things about the person, actions he took, ideas he had, and whatnot. From that comes the ability of 'grok' to mean both 'love' and 'hate'.